Gas turbine engines typically require numerous components to be clamped or bolted to other components. Such components are often (but not exclusively) bearings, stub shafts, discs or gears and these components may, for example, require retention onto a shaft or into a housing.
Currently, standard shaft nuts may be used to secure a component onto a shaft. For example, the shaft nut may be threaded onto the shaft and the component may be held between the shaft nut and an abutment shoulder on the shaft. In order to assemble nut stacks, it may be required to compress the nut stack, to ensure all of the nut stack is fully seated. This is generally done as part of the nut tightening procedure, although there may be occasions when this is done as a separate operation, with a different assembly method or tooling.
There may be friction between the threads of the shaft and the shaft nut and at the contact faces between either side of the component and the shaft abutment shoulder and the shaft nut respectively. However, with current methods there may be galling (e.g. a form of surface damage between sliding faces) and/or surface distress at the contact faces between the component and the shaft abutment shoulder and the shaft nut.
In this respect, lubricants, such as oil or graphite grease may be used to reduce friction at the contact faces between the component and the shaft abutment shoulder and the shaft nut. However, depending on the materials being used and the operating temperatures involved, it may not be possible to use low coefficient of friction lubricants such as graphite grease. Furthermore, the application of lubricants may not be uniform and they may need replenishing with time.
The present invention therefore seeks to address these issues.